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    <title>clCreateContext</title>
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      <div xmlns="" class="refnamediv">
        <a xmlns="http://www.w3.org/1999/xhtml" id="clCreateContext"></a>
        <h1>clCreateContext</h1>
        <p>Creates an OpenCL context.</p>
      </div>
      <div class="refsynopsisdiv">
        <h2></h2>
        <div class="funcsynopsis">
          <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
            <tr valign="bottom">
              <td>
                <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef">cl_context <strong class="fsfunc">clCreateContext</strong>(</code>
                <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="enums.html#cl_context_properties" target="_top">cl_context_properties</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*properties</var>, </td>
              </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">cl_uint</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">num_devices</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td>const <a xmlns="http://www.w3.org/1999/xhtml" class="link" href="abstractDataTypes.html" target="_top">cl_device_id</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*devices</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*pfn_notify</var>
						<code xmlns="http://www.w3.org/1999/xhtml">(</code><div xmlns="http://www.w3.org/1999/xhtml" class="literallayout"><p>const <a class="link" href="scalarDataTypes.html" target="_top">char</a> *errinfo, <br />
						const <a class="link" href="scalarDataTypes.html" target="_top">void</a> *private_info, <br />
						<a class="link" href="otherDataTypes.html" target="_top">size_t</a> cb, <br />
						<a class="link" href="scalarDataTypes.html" target="_top">void</a> *user_data</p></div><code xmlns="http://www.w3.org/1999/xhtml">)</code>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">void</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*user_data</var>, </td>
            </tr>
            <tr valign="top">
              <td> </td>
              <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="_top">cl_int</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*errcode_ret</var><code>)</code></td>
            </tr>
          </table>
        </div>
      </div>
      <div class="refsect1">
        <a id="description"></a>
        <h2>Description</h2>
        <p>
            An OpenCL context is created with one or more devices. Contexts
are used by the OpenCL runtime for managing objects such as command-queues, memory,
program and kernel objects and for executing kernels on one or more devices specified in the
context.
		</p>
      </div>
      <div class="refsect1">
        <a id="parameters"></a>
        <h2>Parameters</h2>
        <div class="variablelist">
          <dl class="variablelist">
            <dt>
              <span class="term">properties</span>
            </dt>
            <dd>
              <p>
                    Specifies a list of context property names and their corresponding values. Each property name is immediately followed by the corresponding desired value. The list is terminated with 0. <code class="varname">properties</code> can be NULL in which case the platform that is selected is implementation-defined. The list of supported <code class="varname">properties</code> is described in the table below. 
                </p>
              <div class="informaltable">
                <table class="informaltable" border="1">
                  <colgroup>
                    <col align="left" class="col1" />
                    <col align="left" class="col2" />
                    <col align="left" class="col3" />
                  </colgroup>
                  <thead>
                    <tr>
                      <th align="left">cl_context_properties enum</th>
                      <th align="left">Property value</th>
                      <th align="left">Description</th>
                    </tr>
                  </thead>
                  <tbody>
                    <tr>
                      <td align="left">
                        <code class="constant">CL_CONTEXT_PLATFORM</code>
                      </td>
                      <td align="left">cl_platform_id</td>
                      <td align="left">Specifies the platform to use.</td>
                    </tr>
                  </tbody>
                </table>
              </div>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">num_devices</code>
              </span>
            </dt>
            <dd>
              <p>
                    The number of devices specified in the <code class="varname">devices</code> argument.
                </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">devices</code>
              </span>
            </dt>
            <dd>
              <p>
                    A pointer to a list of unique devices returned by <a class="citerefentry" href="clGetDeviceIDs.html"><span class="citerefentry"><span class="refentrytitle">clGetDeviceIDs</span></span></a> for a platform.
                </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">pfn_notify</code>
              </span>
            </dt>
            <dd>
              <p>
                    A callback function that can be registered by the application. This callback function will be used by the OpenCL implementation to report information on errors that occur in this context. This callback function may be called asynchronously by the OpenCL implementation.
It is the application's responsibility to ensure that the callback function is thread-safe. If <code class="varname">pfn_notify</code> is NULL, no callback function is registered. The parameters to this callback function are:
                </p>
              <p><code class="varname">errinfo</code> is a pointer to an error string.</p>
              <p><code class="varname">private_info</code> and <code class="varname">cb</code> represent a pointer to binary data that is returned by the OpenCL implementation that can be used to log additional information helpful in debugging the error.</p>
              <p><code class="varname">user_data</code> is a pointer to user supplied data.</p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">user_data</code>
              </span>
            </dt>
            <dd>
              <p>
                    Passed as the <code class="varname">user_data</code> argument when <code class="varname">pfn_notify</code> is called. <code class="varname">user_data</code> can be NULL.
                </p>
            </dd>
            <dt>
              <span class="term">
                <code class="varname">errcode_ret</code>
              </span>
            </dt>
            <dd>
              <p>
                    Returns an appropriate error code. If <code class="varname">errcode_ret</code> is NULL, no error code is returned.
                </p>
            </dd>
          </dl>
        </div>
      </div>
      <div class="refsect1">
        <a id="errors"></a>
        <h2>Errors</h2>
        <p><code class="function">clCreateContext</code> returns a valid non-zero context and <code class="varname">errcode_ret</code> is set to <span class="errorname">CL_SUCCESS</span> if the context is created  successfully. Otherwise, it returns NULL value with the following error
values returned in <code class="varname">errcode_ret</code>:
</p>
        <div class="itemizedlist">
          <ul class="itemizedlist" style="list-style-type: disc; ">
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_PLATFORM</span> if <code class="varname">properties</code> is NULL and no platform could be selected or if platform value specified in <code class="varname">properties</code> is not a valid platform.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_VALUE</span> if context property name in <code class="varname">properties</code> is not a supported property name; if <code class="varname">devices</code> is NULL; if <code class="varname">num_devices</code> is equal to zero; or if <code class="varname">pfn_notify</code> is NULL but <code class="varname">user_data</code> is not NULL.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_INVALID_DEVICE</span> if <code class="varname">devices</code> contains an invalid device or are not associated with the specified platform.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_DEVICE_NOT_AVAILABLE</span> if a device in <code class="varname">devices</code> is currently not available even though the device was returned by <a class="citerefentry" href="clGetDeviceIDs.html"><span class="citerefentry"><span class="refentrytitle">clGetDeviceIDs</span></span></a>.
		</li>
            <li class="listitem" style="list-style-type: disc"><span class="errorname">CL_OUT_OF_HOST_MEMORY</span> if there is a failure to allocate resources required by the OpenCL implementation on the host.
		</li>
          </ul>
        </div>
      </div>
      <div class="refsect1">
        <a id="notes"></a>
        <h2>Notes</h2>
        <p>
            <code class="function">clCreateContext</code> and <a class="citerefentry" href="clCreateContextFromType.html"><span class="citerefentry"><span class="refentrytitle">clCreateContextFromType</span></span></a> perform an implicit retain. This is very helpful for 3rd party libraries, which typically get a context passed to them by the application.
However, it is possible that the application may delete the context without informing the library.
Allowing functions to attach to (i.e. retain) and release a context solves the problem of a context
being used by a library no longer being valid.
        </p>
      </div>
      <div class="refsect1">
        <a id="specification"></a>
        <h2>Specification</h2>
        <p><img src="pdficon_small1.gif" />
            <a href="http://www.khronos.org/registry/cl/specs/opencl-1.0.pdf#page=40" target="OpenCL Spec">OpenCL Specification</a>
        </p>
      </div>
      <div class="refsect1">
        <a id="seealso"></a>
        <h2>Also see</h2>
        <p>
<a class="citerefentry" href="clGetDeviceIDs.html"><span class="citerefentry"><span class="refentrytitle">clGetDeviceIDs</span></span></a>, <a class="citerefentry" href="clCreateContextFromType.html"><span class="citerefentry"><span class="refentrytitle">clCreateContextFromType</span></span></a>,  <a class="citerefentry" href="clRetainContext.html"><span class="citerefentry"><span class="refentrytitle">clRetainContext</span></span></a>,  <a class="citerefentry" href="clReleaseContext.html"><span class="citerefentry"><span class="refentrytitle">clReleaseContext</span></span></a>, 	
<a class="citerefentry" href="clGetContextInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetContextInfo</span></span></a>		
        </p>
      </div>
      <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4>
			Copyright © 
    Copyright © 2007-2009 The Khronos Group Inc. 
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
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the condition that this copyright notice and permission notice shall be included
in all copies or substantial portions of the Materials. 
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